Where do you live in Virginia? I don't believe 8b is a correct zone for anywhere in Va. More like a 6 or a 7. You can grow them in unamended Va. clay, but they'll get larger with better soil. They don't overwinter well in pure clay - it gets waterlogged and they rot. Depending on where you are, what type of canna, and how severe, the winter, you may get some cannas to overwinter outside in semiamended clay.